Tandem gauge wheel assembly for planting unit

ABSTRACT

A seed planting assembly is provided having a plurality of planting units supported by a tool bar, each of which being operable to form a seed trench in soil, plant seeds in the seed trench, and close the seed trench. The seed trench defines a depth that is achieved via a pair of gauge wheels. A press wheel assembly packs the trench after it has been seeded and closed. The planting assembly links the forward gauge wheels with the rear press wheel assembly for reciprocal motion to reduce the trench depth displacement when either a gauge wheel or a press wheel travels over an obstacle.

CROSS-REFERENCE TO RELATED APPLICATIONS

None

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

None

BACKGROUND OF THE INVENTION

The present invention relates to seed planting assemblies in general,and in particular relates to a method and apparatus for maintaining seedtrench depth during operation of a seed planting assembly.

Seed planting units generally include a laterally extending tool barthat supports a plurality of parallel planting units (also known as rowunits). The tool bar is typically coupled to a tractor or like vehiclesuitable for towing the planting assembly along a field that is to beseeded to a crop. Each planting unit includes a device for opening aseed trench in the ground as the tractor draws the tool bar across afield to be seeded.

Each planting unit further includes a seed meter to dispense seeds at acontrolled rate into a seed trench as the meter is advanced above andalong the seed trench during operation. Generally, seeds are deliveredto the metering assembly from a seed hopper located on the planting unitor, alternatively, from a smaller container fed from a centralized largehopper used to feed all or a portion of the planting units. Eachplanting unit further includes a closing assembly that moves soil at thesides of the seed trench to close the seed trench over the plantedseeds. Adjacent planting units are laterally spaced a sufficientdistance to form seed trenches that are spaced a corresponding distanceapart that is suitable for the type of seed being planted.

Typically a pair of gauge wheels are disposed adjacent the outersurfaces of the seed trench-opening device. The height of the gaugewheels relative to the seed trench-opening device generally is set bythe user, which thereby predetermines the depth of the seed trench.However, when one of the gauge wheels travels over an obstacle that iselevated with respect to the soil, such as a rock, hard lump of dirt,heavy residue, and the like, the planting unit will rise, therebydecreasing the seed trench depth. If the planting unit is traveling at asufficient speed, the planting unit may become momentarily airborne,thereby further lifting the seed trench-opening device out of theground.

It should be appreciated that a crop yield is maximized when all seedsemerge from the soil within a given timeframe relative to each other.Otherwise, if some seeds emerge later than others in a given row, theyield for that row can be substantially reduced. One known method forencouraging uniform seed emergence is to maintain the seed trench aconstant depth when performing seed planting operations. Some plantingunits include a bracket that links the pair of gauge wheels.Accordingly, when one gauge wheel travels over an obstacle, the opposinggauge wheel to lower and maintain contact with the soil, therebydecreasing the seed trench depth by a distance equal to one-half theheight of the obstacle. Conversely, when one of the gauge wheels travelsover a depression, the opposing gauge wheel is raised an equal distance,thereby increasing the seed trench depth by a distance equal to one-halfthe depth of the depression. Such a system is described in U.S. Pat. No.4,423,788.

While the above system has proved suitable for its intended purpose, itwould be desirable to provide a method and apparatus for furtherreducing the change in seed trench depth when traveling over an obstacleor in a depression while performing seed planting operations.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a seed plantingunit includes a planting frame. The frame carries A) a seed trenchopening assembly including a seed trench forming member operable tocreate a seed trench in a ground surface, B) a seed delivery assemblydelivering seeds into the seed trench, and C) a seed trench closingassembly operable to close the seed trench. The planting unit furtherincludes a planting unit support assembly including A) a pair ofopposing gauge wheels in mechanical communication with the frame, and B)a rear press wheel assembly in mechanical communication with the gaugewheels. A vertical displacement of the gauge wheel or press wheels in afirst direction produces a biasing force on the other of the gauge andpress wheel in a direction opposite the vertical displacement.

The foregoing and other aspects of the invention will appear from thefollowing description. In the description, references are made to theaccompanying drawings which form a part hereof, and in which there isshown by way of illustration, and not limitation, a preferred embodimentof the invention. Such embodiment does not necessarily represent thefull scope of the invention, however, and reference must therefore bemade to the claims for interpreting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is hereby made to the following figures in which likereference numerals correspond to like elements throughout, and in which:

FIG. 1 is a schematic perspective view of a seed planting assemblysupporting a plurality of seed planting units constructed in accordancewith the preferred embodiment of the invention;

FIG. 2 is a side elevation view of a planting unit illustrated in FIG. 1constructed in accordance with the preferred embodiment of the inventionas it approaches an obstacle;

FIG. 3 is a side elevation view of the planting unit illustrated in FIG.2 showing an enlarged view of the down pressure assembly and seed trenchopening assembly;

FIG. 4 is an assembly view of components of the down pressure assemblyillustrated in FIG. 3;

FIG. 5 is a top plan view of the assembled down pressure assemblyillustrated in FIG. 4;

FIG. 6 is a sectional side elevation view of the down pressure assemblytaken through line 6-6 of FIG. 5;

FIG. 7 is a sectional side elevation view of the down pressure assemblytaken through line 7-7 of FIG. 5;

FIG. 8 is a sectional elevation view of the down pressure assembly takenthrough line 8-8 of FIG. 6 illustrating a neutral gauge wheel position;

FIG. 9 is a sectional side elevation view similar to FIG. 8, butillustrating an offset gauge wheel position;

FIG. 10 is a side elevation view of the planting unit illustrated inFIG. 2 as the planting unit travels over the obstacle;

FIG. 11 is an end elevation view of the seed trench opening assembly ofthe planting unit taken along the line 11-11 of FIG. 2;

FIG. 12 is an end elevation view of the seed trench opening assembly ofthe planting unit along the line 12-12 of FIG. 10;

FIG. 13 is a side elevation view of a planting unit constructed inaccordance with an alternate embodiment of the invention;

FIG. 14 is a side elevation view of a planting unit constructed inaccordance with another alternate embodiment of the invention;

FIG. 15 is a sectional side elevation view of a rear press wheeladjustment mechanism taken along the line 15-15 of FIG. 14;

FIG. 16 is a top plan view of the rear press wheels constructed intandem in accordance with an alternate embodiment of the invention;

FIG. 17 is an end view of the rear press wheels illustrated in FIG. 16as they approach an obstacle; and

FIG. 18 is a view similar to FIG. 17 as one of the press wheels travelsover the obstacle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a seed planting assembly 20 includes a laterallyextending toolbar 22 connected at its middle to a forwardly extendingtow bar 24. Tow bar 24 includes a connector 27 disposed at itslongitudinally forward end and configured to mate with a correspondinghitch, or the like, of a towing tractor (not shown). Toolbar 22 issupported by a chassis 26 that is connected to tow bar 24 via a bracketassembly 34. Chassis 26 is supported on the ground by two pair of innerwheels 28 disposed on opposite sides of tow bar 24, and a pair of outerwheels 30 disposed proximal the opposing laterally outer ends 32 oftoolbar 22.

A plurality of seed planting units (or row units) 36 extendslongitudinally rearwardly from toolbar 22. In particular, referring alsoto FIG. 2, each planting unit 36 includes a frame 37 that is connectedat its front end 39 to toolbar 22 via a mounting assembly 59. Mountingassembly includes a pair of upper support beams 61 (one illustrated) anda pair of lower support beams 63 (one illustrated) that are hingedlyconnected to frame 37 at one end, and to a mounting structure 55 atanother end. Mounting structure 55 is, in turn, connected to toolbar 22.Support beams 61 and 63 thus enable planting unit 36 to be raised andlowered without changing the orientation of the planting unit.

As is well-known in the art, planting units 36 are mounted in aside-by-side (lateral) relation relative to each other along the toolbar22. While sixteen such row units are illustrated in FIG. 1, the presentinvention contemplates that up to thirty-one row units or more can betypically assembled on a single toolbar 22 in accordance with thepreferred embodiment. During operation, forward movement of the tractorcauses row units 36 to ride along the ground, forming a plurality ofseed trenches that receive seeds and are subsequently closed.

Referring to FIG. 2 in particular, each planting unit 36 preferablyincludes a conventional seed trench opening assembly 38, each of whichincluding a pair of laterally spaced seed trench opener discs 40 thatconverge forwardly and downwardly to define a convergence point 41 thatcreates a seed trench 45 planting unit 36 travels along the ground 85.As illustrated in FIG. 2, seed trench 45 has a depth D1 that is definedherein as a desired seed trench depth. Opener discs 40 are rigidlymounted to frame 37 via bracket 31. A pair of gauge wheels 43 isprovided that are spaced laterally outwardly on either side of openerdiscs 40. Gauge wheels 43 rotate about hub 64 as planting unit 36travels along the ground 85.

Each planting unit 36 further includes a seed trench firming point 42disposed rearwardly from convergence point 41. An opener shoe 44 isdisposed rearwardly from firming point 42. Opener shoe 44 and firmingpoint 42 can be integrally connected to each other. Firming point 42extends slightly downwardly with respect to the opener shoe 44, andhelps create and define a trench in the middle of the seed trench 45formed by opening discs 40. Alternatively, the planting unit 36 can beprovided with a runner opener type, or alternative opener apparatus,suitable for providing a seed trench in the ground as is appreciated byone having ordinary skill in the art. Planting unit 36 further includesa pair of spring-loaded seed-trench closer discs 46 disposed rearwardlyfrom opener shoe 44. A press wheel assembly 35 can include one or morepress wheels 48 (preferably a pair of press wheels as illustrated inFIG. 16), and is disposed rearwardly from closer discs 46. The presswheels 48 rotate as planting unit 36 travels along ground 85. Presswheels 48 and closer discs 46 are biased against the ground 85 by spring51.

Planting unit 36 further includes a seed hopper 50 that provides storagefor seed material that is to be gravitationally deposited into the seedtrench that is formed as the seed trench opening assembly moves acrossthe field during operation. It should be appreciated, however, that ahopper container, smaller than container 50, can alternatively beconnected to a centralized bin or large hopper in a conventional manner.In the illustrated embodiment, seeds are delivered from hopper 50 to aseed metering assembly 52 that acts under vacuum pressure to deliver theseeds into a seed tube 54 at a uniform rate. Seed tube 54 defines aconduit having an outlet end immediately downstream of opener shoe 44and upstream of seed trench closer discs 46. Seed tube 54 thus receivesseeds from metering assembly 52 and defines a substantially verticalpassage through which the seeds are delivered into the seed trench, andpreferably the trench formed by opener shoe 44. The components of seedmetering assembly 52 are further described in U.S. Pat. No. 6,109,193,the disclosure of which is hereby incorporated by reference.

A tandem wheel arm 47 extends between each gauge wheel 43 and presswheel assembly 35 that mechanically links the front gauge wheels 43 withthe rear press wheels 48. In particular, the front end of wheel arm 47is connected to the outer surface of gauge wheel at gauge wheel hub 64.Arm 47 extends rearwardly from the front end, and defines a rear endthat is connected to press wheel assembly 35 at press wheel hub 49.

Referring also to FIG. 3, tandem wheel arm 47, and therefore gaugewheels 43 and press wheel 48, is connected to planting unit frame 37 viaa gauge wheel arm 56. Gauge wheels 43 and press wheel assembly 35 arethus suspended independently of opener discs 40. Each gauge wheel arm 56includes a lower segment 58 that is pivotally connected to the middle ofpress wheel 48 at a joint 65. Gauge wheel arm 56 further includes anupper segment 60 defining an upper gauge wheel arm end 66. Upper segment60 is integrally connected to lower segment 58 at an elbow 70 thatdefines a fixed angle between lower and upper segments 58 and 60. Elbow70 is pivotally mounted onto frame 37. Vertical translation of gaugewheels 43 or press wheel 48 relative to frame 37 causes the tandem wheelarms 47 and corresponding gauge wheel arms 56 to pivot about elbow 70,thereby causing the upper ends 66 to translate forwardly and rearwardly.

During operation, as the power source or tractor pulls the tool bar 22across and over the ground, the seed trench opening assembly 38 opens aseed trench in the ground. Seeds from the hopper 50 flow into the seedmetering assembly 52 in bulk and are subsequently deposited into theseed trench via seed delivery tube 54 at a controlled rate. The seedtrench closer discs 46 trail the seed trench opening assembly 38 and, asthe seed planting unit 36 is drawn across the field, close the seedtrench together and over the seed dispensed by the seed meteringassembly 52. The trailing press wheels 48 firm the soil closed over thedelivered seeds.

Planting unit 36 can also be equipped with a pesticide hopper 57 that ismounted towards a rear end of the planting unit. Hopper 57 preferablyincludes an insecticide and/or herbicide, and is provided withconventional dispensing apparatus for applying controlled amounts ofinsecticide where desired in combination with the planting of seeds byeach planting unit 36.

Referring again to FIG. 1, each planting unit 36 can be coupled to anair moving system 76 that includes one or more air moving units(collectively identified as 78) enclosed in one or more housings(collectively identified as 80). While air mover unit(s) 78 areconfigured to provide negative pressure, they can alternatively functionas blower units if a positive pressure seed metering assembly isimplemented in planting units 36. Air moving system 76 includes a lowerlateral tubing member 82 that is connected at its middle to one of theair moving units 78, and extends laterally outwardly therefrom in bothdirections. A plurality of openings (not shown) are formed in tubingmember 82 that connect to a forward end of a corresponding plurality offlexible intake tubes that, in turn, connect with the correspondingmetering assembly 52.

A bifurcated arrangement is illustrated with respect to a pair of upperlateral tubing members 84 that are connected at their laterally innerends to one or more air mover units 78. Tubing members 84 extendparallel to, and are disposed above, tubing member 82, and are connectedat their outer ends to outer tubing members 86. Outer tubing members 86are vertically aligned with lower tubing member 82, and extend acrossthose planting units 36 that are disposed laterally outwardly withrespect to lower tubing member 82. A plurality of openings (not shown)are formed in tubing members 86 that connect to a plurality of flexibleintake tubes that, in turn, connect with the metering assemblies 52 oflaterally outwardly disposed planting units 36.

During operation, air moving units 78 draw air through the meteringassemblies 52 of all planting units 36 to which the lateral tubes 82-86are operably connected. The number of air mover units 78 implemented ina given seed planting assembly depends largely on the number of plantingunits 36 and the airflow rating of each air mover unit.

Referring now to FIGS. 2 and 3, planting unit frame 37 includes acentral longitudinally extending column 72 that houses a tension bar 74that extends generally along the entire length of column 72. Tension bar74 includes a cylindrical member 92 extending forwardly from therearward end 88 of column 72. Member 92 is threadedly connected torearward end 88. The forward end of member 92 is rotatably connected toa plate 93 which is, in turn, connected to a pair of laterally spacedparallel links 94 that flank seed delivery tube 54, and are connected attheir forward ends to a rectangular housing 96 which extendslongitudinally forwardly of column 72. Housing 96 is connected at itsforward end to a cylindrical member 98, which defines the forward end oftension bar 74. Cylindrical member 98 defines a threaded forward end 101that is inserted into a threaded aperture 100 that extendslongitudinally through a rectangular plate 102 to provide a terminalstop (See also FIG. 4).

A depth adjustment knob 90 extends rearwardly from the rearward end 88of column 72, and is attached to tension bar 74. Accordingly, depthadjustment knob 90 can be actuated clockwise and counterclockwise totranslate all components of tension bar 74 forwardly and rearwardly,respectively. Longitudinal translation of tension bar 74 adjusts thedesired depth of seed trench 45, as will be described in more detailbelow. Knob 90 can be actuated manually, or alternatively can beconnected to an actuator that is controlled electronically from withinthe tractor or other towing implement. The present inventioncontemplates several alternative geometric variations of tension bar 74that enables forward and rearward translation. For instance, knob 90could alternatively be positioned at the forward end 39 of planting unitframe 37.

Referring to FIG. 3 in particular, planting unit 36 includes anautomatic down pressure assembly 104 for automatically adjusting thedown pressure acting against frame 37 as the planting unit travelsbetween areas of different ground hardness during operation. Inparticular, assembly 104 includes a valve 110 that is actuated byforward and rearward movement of upper gauge wheel arm ends 66. Valve110 includes a port 107 (see FIG. 4) that is connected to a compressedair source 111 (such as an air compressor or charged air reservoir) viaa conduit 113. Valve 110 further includes a second port 109 that isconnected to a spring member 114 via a conduit 115. Air source 111 ispreferably centrally mounted onto tool bar 22, and provides compressedair to one or more row units 36. Alternatively, air source 111 could beprovided by the air braking system of the tractor (not shown) that towsplanting assembly 20 during operation. Spring member 114 is fastened toa mounting bracket 116, which extends upwardly from mounting structure55. It should thus be appreciated that spring member 114 is connectedto, and grounded at, tool bar 22. However, the present inventionenvisions alternative constructions for connecting spring member 114 totool bar 22, either directly or indirectly. The present inventionfurther contemplates that source 111 can alternatively provide any fluidcapable of inflating and deflating spring member 114, as appreciated byone having ordinary skill in the art.

Spring member 114 defines a bottom surface 117 that is connected to adownwardly extending piston 118. Piston 118, in turn, is pivotallyconnected to lower link 63 at a lower piston end 120. Piston 118 isfurther connected to upper link 61 at a location between lower end 120and bottom surface 117. In particular, a pair of apertures 122 and 124extends laterally through links 61 and 63, respectively. A pin or othersuitable fastener extends through apertures 122 and 124, along withmating apertures (not shown) extending through piston 118. Spring member114 is mounted to bracket 116 in such a way to allow bottom surface 117to translate vertically downwardly and upwardly as the pressure insidespring member 114 increases and decreases, respectively. Spring member114 is thus also referred to herein as a fluid spring, as the internalspring pressure is varied as fluid is delivered to, and removed from,the spring member.

Referring now to FIG. 4 in particular, a longitudinally elongated groove106 extends vertically through cylindrical member 98 at a locationproximal housing 96. A square housing 126 defines a pair oflongitudinally opposing end walls 128 and opposing upper and lower walls130. An aperture 132 extends longitudinally through end walls 128, anddefines a diameter that is larger than the diameter of cylindricalmember 98. Housing 126 further defines an aperture 134 extendingvertically through upper and lower walls 130. Aperture 134 has adiameter that is less than the lateral thickness of elongated groove106.

A wobble bracket 136 includes a central hub 138 that defines a laterallyextending front end wall 140. Opposing upper and lower walls 142 extendrearwardly from end wall 140, and include a forward rectangular section144 integrally connected to a rearwardly disposed arced section 146. Aside wall 148 extends along the periphery of walls 142 to join opposinglaterally outer ends of end wall 140. Side wall 148 thus also definesopposing rectangular portions 150 and an arced portion 152 connectingrectangular portions 150. Arced portion 152 provides a convex surfacewith respect to the longitudinally rearward end of bracket 136.

A void 154 having a rectangular cross-section extends longitudinallythrough front end wall 140 and arced side wall 152. Void 154 is sized toloosely receive housing 126. A cylindrical aperture 156 extendsvertically through the arced sections 136 of upper and lower walls 142.Aperture 156 has a diameter substantially equal to the diameter ofaperture 134. A pair of wings 158 extends laterally outwardly fromrectangular portions 150 of side wall 148. Each wing 158 includes aleading edge 159 that extends laterally outwardly from side wall 148. Atrailing edge 160 is disposed rearwardly from leading edge 159, and isangled forwardly from a first end 162 proximal side wall 148 to a distalend 164.

A coil spring 166 extends rearwardly from plate 102. Spring 166 has anouter diameter sized to abut front end wall 140.

Referring now also to FIGS. 5-8, down pressure assembly 104 is assembledby at least partially inserting housing 126 into void 154 through arcedportion 152 of side wall 148, such that end walls 128 extend parallel tofront end wall 140 and perpendicular to rectangular sections 150 of sidewall 148. Housing 126 is inserted until aperture 134 is in alignmentwith aperture 156. Housing 126 is then mounted onto cylindrical member98 by sliding the housing 126 rearwardly such that front end 101 extendsthrough aperture 132 formed in rear wall 128. Housing 126 is furtherslid rearwardly along cylindrical member 98 until apertures 134 and 156are aligned with groove 106.

A pin 168 is provided including a cylindrical shaft 169 that defines anupper end 170 and a lower end 172, and has a diameter slightly less thanthe diameter of apertures 134 and 156. Pin includes an annular shoulder174 extending radially outwardly from upper end 170. The outer diameterof shoulder 174 is greater than the diameter of apertures 134 and 156.An arm 176 extends vertically upwardly from upper end 170, and thusextends upwardly beyond shoulder 174. A keyhole 178 extends radiallythrough lower end 172, and is sized to receive the shaft end 180 of akey 182.

During installation, the lower end 172 of pin 168 is inserted throughaperture 156 in upper wall 142, and subsequently through aperture 134 inupper wall 130. Pin 168 is slid downwardly until lower end extendsthrough groove 106, and apertures 134 and 156 in lower walls 130 and142, respectively, until key hole 178 emerges from lower wall 142.Shoulder 174 abuts upper wall 142 to prevent pin 168 from being insertedcompletely through bracket 136. Shaft 180 is then inserted into key hole178 to lock the pin 168 in position. Shaft 180 may be locked in keyhole178 by any method known in the art. The permissible longitudinal travelof wobble bracket 136 is limited by the longitudinal length of groove106.

Void 154 is sized larger than housing 126 by a predetermined amount soas to enable bracket 136 to pivot clockwise and counterclockwise aboutpin 168. In accordance with the preferred embodiment, bracket 136 ispermitted to pivot 35° equally back and forth (for a total travel of70°), though any angle of travel between 0° and 180° is contemplated bythe present invention. For instance, referring to FIGS. 8 and 9, duringoperation on level terrain, both upper ends 66 exert the same force ontrailing edges 160, thereby preventing rotation of wobble bracket 136.However, when one of the gauge wheels 43 (the right gauge wheel 43 asillustrated) travels over an obstacle 67 (See FIG. 10) that is elevatedwith respect to the terrain under the opposing gauge wheel, thecorresponding arm 47 will rise, thereby causing upper end 66 totranslate forwardly, and the opposing upper end 66 to translaterearwardly, as described above. The motion of right upper end 66 causesbracket 136 to rotate counterclockwise in the direction of Arrow A. Theopposing force of left upper end 66 reduces the relative verticaltranslation of gauge wheels 43, and furthermore prevents actuation ofvalve 110 in response to the forward motion of only one upper end 66.

Spring 166 is then slid rearwardly over the forward end 101 ofcylindrical member 98 until the rear face of spring 166 abuts front face140. Plate 102 is then threadedly inserted onto the forward end 101 ofcylindrical member 98 by rotating plate 102 in a clockwise direction(taken from a rearward view of plate 102). Plate 102 is inserted untilthe forward end of spring 166 engages plate 102, and the rearward end ofspring 166 engages forward end wall 128. Plate is then continuouslyinserted until spring 166 is sufficiently compressed. It should thus beappreciated that spring 166 resists forward translation of bracket 136.

Each gauge wheel arm 56 is laterally and vertically aligned with wings136. The upper end 66 of each gauge wheel arm 56 extends substantiallyvertically upwardly, and defines a flat surface 62 that is recessed andconfigured to abut trailing edge 160 of each wing. Accordingly, as agiven gauge wheel 43 is raised and lowered relative to the oppositegauge wheel 43 during operation, for instance as planting unit 36travels over uneven terrain, the corresponding upper end 66 will travelforwardly and rearwardly with respect to the opposite upper end 66. Theupper end movement forces wobble bracket 136 to pivot about pin 168. Theangular compliance of bracket 136 reduces the seed trench depth varianceduring a planting operation. Furthermore, upward translation of gaugewheels 43 relative to frame 37 is permitted, though resisted, by spring66, which directly resists forward translation of bracket 136. Downwardtranslation of gauge wheels 43 relative to frame 37 biases surfaces 62rearwardly away from trailing edges 160, thereby allowing spring 166 tobias wobble bracket 136 rearwardly against surfaces 62.

As described above, depth adjustment knob 90 is rotatable clockwise orcounterclockwise to translate cylindrical member 98 towards or away fromfront 39 of frame 37. When member 98 is translated towards front offrame 37, wobble bracket 136 is biased towards spring 166, therebyenabling gauge wheel arm ends 66 to translate forwardly, thereby raisinggauge wheels 43. When gauge wheels 43 are raised, seed trench firmingpoint 42 is lowered relative to the gauge wheels, which increases thedepth of seed trench 45. Likewise, when member 98 is translated awayfrom the front end 39 of frame 37, the spring force biases bracket 136rearwardly, thereby lowering the gauge wheels 43 and raising the seedtrench firming point 42 relative to the gauge wheels which, in turn,decreases the depth of seed trench 45. Once set, the seed trench 45 hasa desired depth D1 when the gauge wheels 43 ride along the ground undera predefined vertical force (down pressure) that maintains groundcontact, but is not excessive, which forces gauge wheels 43 into theground, thus unnecessarily compacting the soil adjacent the seed trench45.

A pair of laterally spaced apertures 184 extend vertically downwardlyinto the front end of housing 96. Apertures 184 are laterally spaced soas to be positioned at opposite lateral ends of housing 96. A valvemounting bracket 186 is provided having a base 188 that extendslaterally in a horizontal orientation. Base 188 is integrally connectedto a side wall 190 that extends vertically upwardly from one lateral endof base 188. A support wall 192 is also provided that extends forwardlyin a vertical orientation, and is connected at its rearward end to sidewall 190 via screws 193. A portion 194 of support wall 192 thus extendsforwardly with respect to base 188. Referring to FIG. 6, screws 193 canbe mounted in any position along corresponding longitudinally extendingslots 195 that are formed in support wall 192. The longitudinal positionof bracket 186 (and hence valve 101) is thus adjustable, therebyenabling a user to preset the down pressure applied to frame 37 andgauge wheels 43, as will become apparent from the description below.

Referring again to FIGS. 5-8, the lateral position of bracket 186 (andhence valve 101) is also adjustable. In particular, a first elongatedslot 196 extends through base 188 and are positioned proximal the frontedge of base 188 at the laterally outer edge that is opposite side wall190. A second elongated slot 196′ is disposed proximal the front end ofbase 188 (forwardly aligned with slot 96) and is disposed proximal sidewall 190. The two slots are displaced from each other a distance equalto the distance between apertures 184. A pair of screws 200 are providedthat can be inserted through slots 196 and 196′ and threadedly insertedinto apertures 184. Accordingly, the lateral position of bracket 186 isadjustable by mounted the bracket in any position accommodated by slots196 and 196′.

Valve 110 includes a first proximal side wall 202 that is mounted ontothe laterally inner surface of side wall 190 by any suitable attachmentmechanism. A second distal side wall 204 is disposed opposite side wall202. Conduits 113 and 115 extend outwardly from side wall 202 andconnect to air source 111 and spring 114, as described above, along withan outlet 206 to the ambient environment.

A valve arm 208 is provided having a cylindrical neck 210 that extendsupwardly from a horizontal arm 212. Neck 210 extends into the bottom ofvalve 110 such that arm 212 extends horizontally outwardly from neck 210below valve 110. A horizontally elongated groove 213 extends verticallythrough arm 212, and is sized to receive arm 176 of pin 168. When valve110 is installed on mounting bracket 186, and when bracket 186 ismounted onto housing 96, arm 176 extends laterally outwardly from neck210 in a direction opposite side wall 190. Arm 176 is translatedlongitudinally forwards and backwards during operation, thereby causingvalve arm 212 to pivot clockwise and counterclockwise, respectively,(from a downward view) about neck 210 during operation to control fluidflow through valve 110, as will be described in more detail below.

Valve 110 is a variable flow valve, and can be of the type described inU.S. Pat. No. 4,726,571, the disclosure of which is hereby incorporatedby reference as if set forth in its entirety herein. Alternatively, askilled artisan will appreciate that valve 110 can be of any suitableconstruction capable of operating as described herein. In a first mode,when valve arm 208 is in a neutral, pivotally centered position, flow inand out of ports 113 and 115 is blocked. Accordingly, when the valve isconnected to source 111 and spring 114 in the manner described above,flow from source 111 is blocked from travelling to spring 114, and airin spring 114 is prevented from flowing through valve 110 and into theambient environment through outlet 206.

In a second mode, when valve arm 208 is rotated clockwise (from a viewlooking down), port 107 continues to be blocked, but port 109 is coupledto outlet 206. Accordingly, air is permitted to flow from spring 114into the ambient environment via outlet 206. It should be appreciatedthat removing air from spring 114 reduces the spring pressure andcorrespondingly reduces the downward force (down pressure) that the airspring 114 exerts on frame 37. Because valve 110 is a variable flowvalve, the flow rate of air through the valve 110 from spring 114 willincrease as arm 208 is pivoted clockwise.

In a third mode, when valve arm 208 is rotated counterclockwise (from aview looking down) from the neutral position, port 109 is blocked, butport 107 is linked to port 109, thereby permitting air to flow fromsource 111 through valve 110 and into spring 114. It should beappreciated that increasing airflow into the spring 114 increases thespring pressure, and correspondingly increases the downward force thatspring 114 exerts on frame 37. Because valve 110 is a variable flowvalve, the flow rate of air travelling from source 111, through valve110, and to spring 114 will increase as arm 208 is pivotedcounterclockwise.

As described above, the position of bracket 186 (and hence valve 110) isadjustable in the lateral direction. For instance, when bracket 186 ismounted in the innermost lateral position (i.e., screws 200 are disposedtowards wall 192), arm 176 engages groove 213 at a location proximalneck 210. The location of arm 176 engagement with groove 213 moveslaterally away from neck 210 as bracket 186 is mounted in positionslaterally outwardly from the innermost lateral position. It should beappreciated that longitudinal translation of pin 168 will cause arm 212to pivot increasingly as pin 176 engages groove 213 at locations closerto neck 210. Accordingly, valve 110 is most sensitive when mounted inthe innermost lateral position described above, and becomes lesssensitive as bracket 186 is mounted at positions laterally outwardlyfrom that position. The sensitivity of the automatic pressure system istherefore advantageously adjustable, as will be appreciated from thedescription below. Because valve 110 is a variable flow valve, the flowrate of air from source 111 to spring 114 will increase as arm 208 ispivoted counterclockwise.

Also, as discussed above, the position of bracket 186 (and hence valve110) is adjustable in the longitudinal direction. As a result, once knob90 is actuated to determine the desired seed trench depth, the desireddown pressure can be predetermined. In particular, as bracket is mountedin a longitudinally forward position relative to pin 168, valve arm 208will pivot counterclockwise, thus allowing air to flow from source 111to spring 114 and increasing the down pressure on frame 37. Conversely,as bracket 186 is mounted in a longitudinally rearward position relativeto pin 168, valve arm 208 will pivot clockwise, thus allowing air toflow from spring 114 and decreasing the down pressure.

As discussed above with reference to FIG. 2, it is desirable to maintainthe down pressure acting against frame 37 at a level that produces aseed trench 45 having the desired depth. However, when planting unit 36travels into softer terrain or when the planting unit rate of traveldecreases, the down pressure will force the opener discs 40 and gaugewheels 43 to sink deeper into the ground 85 and cause seed trench 45 tohave a depth greater than the desired depth. Less down pressure isdesired in this situation. Because the upward vertical forces that theground 85 imparts on the opener discs will decrease in this situation,the upward forces acting on the gauge wheels 43 will increase, therebycausing the upper ends 66 of gauge wheel arms 56 (along with pin 168) totranslate forwardly. Valve arm 208 is then rotated clockwise, enablingair to flow from spring 114 into the ambient environment via outlet 206.As air is removed from spring 114, the downward spring force is reduced,thereby reducing the down pressure applied to frame 37 by spring 114.

As the down pressure against frame 37 is reduced, opener discs 40 andgauge wheels 43 begin to rise within the ground 85, thus causing upperends 66 to translate rearwardly. Valve arm 208 thus pivotscounterclockwise towards the neutral position, causing a reduction inthe air flowing out of the spring 114. Once the discs 40 and gaugewheels rise to a position such that seed trench 45 has a desired depthD1, the valve arm 208 will be in the neutral position, and the downpressure will be maintained.

Otherwise, when planting unit 36 travels over hard terrain, or travelsat faster speeds, opener discs 40 will tend to rise within the ground,thereby causing the planting unit 36 and gauge wheels 43 to rise aswell. The trench depth thus becomes less than the desired depth D1. As aresult, increased down pressure is required to ensure that sufficientgauging is achieved by gauge wheels in order to create the desiredtrench depth D1. Gauge wheels 43, which constantly ride along the ground85 under the force of spring 166, are lowered relative to planting unitframe 37, thereby causing the upper ends 66 of corresponding gauge wheelarms 56 (and pin 168) to translate longitudinally rearwardly under theforce of spring 98.

Rearward translation of pin 168 within groove 106 causes valve arm 208to rotate counterclockwise, thereby coupling ports 113 and 115 andallowing air to flow from source 111 to spring 114. The increased airpressure within spring 114 biases piston 118 downwardly, therebyincreasing the down pressure on frame 37. As the down pressureincreases, opener discs 40 and gauge wheels 43 will be forced furtherinto the ground, thereby increasing the depth of seed trench 45. Theupper ends 66 will thus translate forwardly and valve arm 208 willrotate clockwise towards the neutral position. As arm 208 rotatesclockwise, valve 110 will cause the air flow from source 111 to spring140 to decrease, thereby slowing the rate of opener disc and gauge wheeldescent as the seed trench depth approaches the desired depth. Air flowto and from spring 140 will be blocked once the desired down pressure isapplied to the frame (and gauge wheels 43), thereby achieving thedesired seed trench depth. The valve arm 108 will be in the neutralposition based on the previous setting.

It should be appreciated that while the gauge wheels 43 provide a depthregulating member in accordance with the preferred embodiment, thepresent invention contemplates that any suitable depth regulatingmember, for example a skid or a plate or the like, that is capable ofriding along the ground 85 to regulate trench depth is contemplated bythe present invention.

The present invention further recognizes that it may be desirable toregulate the maximum air pressure in spring 114 in order to preventoverpressurization of the spring and subsequent failure. Accordingly, apressure relief valve (not shown) can be disposed in conduit 115proximal spring 114 that redirects air from valve 110 to the ambientenvironment when the pressure within the spring exceeds a predeterminedthreshold. Pressure relief valves of this type are well known to thosehaving ordinary skill in the art.

Advantageously, valve 110 can include an internal delay system thatprevents the valve from changing modes for a predetermined period oftime. Accordingly, down pressure on the frame is not adjusted until theseed trench depth has deviated from the desired depth for the period oftime. The delay prevents abrupt changes in down pressure when, forinstance, the planting unit 36 momentarily travels over obstacle 67 oruneven terrain.

It should be appreciated the down pressure assembly 104 advantageouslyenables a user to perform planting operations at various speeds and overvarious terrain while maintaining a constant desired seed trench depthwithout having to manually adjust the down pressure on the plantingunit.

Referring now to FIGS. 10-12, the tandem wheel arm 47 enables reciprocalmovement between the press wheel(s) 48 and gauge wheels 43. Furthermore,wobble bracket 136 enables reciprocal movement between gauge wheels 43.Moreover, press wheels 48 can be provided in tandem to enable reciprocalmovement between press wheels 48, as is described in more detail below.These reciprocal movement assemblies, both alone and in combination,reduce variations in seed trench depth with respect to conventionalplanting units 36 when one of the gauge wheels 43 travels over anobstacle 67 having a height H, as will now be described.

In particular, referring also momentarily to FIG. 2, as gauge wheels 43approach the obstacle 67, opener discs 40 are creating a seed trench 45at the desired depth D1. However, when one of the gauge wheels 43 (theright gauge wheel 43 as illustrated in FIG. 12) travels over theobstacle 67 having a height H and is thus translated upwardly, arm 47pivots about joint 65, thereby biasing the corresponding press wheel 48downwardly a distance equal to H. However, ground 85 does not permit thecorresponding press wheel 48 to travel downwardly. Accordingly, becausejoint 65 is located at the longitudinal midpoint between gauge wheel 43and press wheel 48, and because press wheel 48 continues to ride alongthe ground 85, joint 65 is raised a distance equal to ½*H.

When joint 65 is translated upwardly, gauge wheel arm 56 pivots aboutelbow 70, thereby biasing upper end 66 forwardly a distancecorresponding to the ½*H vertical travel of joint 65. The upper end 66of the left gauge wheel arm 56 is thus biased rearwardly by wobblebracket 136 which biases the left joint 65 downwardly a distance equalto ½*H.

However, ground 85 prevents the left gauge wheel 43 from travelingdownwardly a distance equal to ½*H. As a result, upper ends 66 andwobble bracket 136 are translated forwardly an amount that correspondsto the planting unit being raised a distance of ¼*H, which providesclearance for the opposing gauge wheel 43 to be lowered by a distanceequal ¼*H. The cumulative effect of the ¼*H forward movement of wobblebracket 136 and the downwards translation of the opposing gauge wheel of¼*H offsets the ½*H distance that the right upper end 66 was biasedforwardly in response to traveling over obstacle 67. Wobble bracket 136thus operates as a mechanical linkage in a manner similar to tandemwheel arm 47, except that wobble bracket 136 links the left and rightelbows 70, which are connected to the planting unit frame 37. As aresult, when the right joint 65 is translated upwardly a distance of½*H, the wobble bracket 136, which is located at the midpoint betweenelbows 70, produces an overall upwards translation of planting unitframe 37 (and thus opener discs 40) of ¼*H. Tandem wheel arms 47 thusenable the seed trench 45 to maintain a more constant depth thanachieved by conventional planting units.

If, on the other hand, the rear press wheel 48 travels over obstacle 67having height H, linkage 47 biases both gauge wheels 43 downwardly.However, because ground 85 does not permit downward movement of gaugewheels 43, midpoint 65 is raised a distance equal to ½*H. Because bothgauge wheels 43 remain engaged with ground 85 as they are biaseddownwardly, the wobble bracket 136 does not further reduce the verticaldisplacement. Accordingly, planting unit frame 37 (and opener discs 40)are raised a distance equal to ½*H.

Referring also to FIGS. 16-18, the present invention contemplates thatplanting unit 36 illustrated in FIG. 10 can include a press wheelassembly 35 having a pair of press wheels 48 that are rotatablyconnected to the outer ends of a laterally extending axle 79. While thepress wheels 48 are illustrated in a vertical orientation, it should beappreciated that they could alternatively ride along the ground 85 at anangle between 0° and 40° (with the wheels converging in a downwarddirection) with respect to the vertical orientation illustrated.Alternatively, or in addition, press wheels 48 could converge in adirection from front-to-rear at an angle between 0° and 40°.

A collar 81 is disposed on axle 79, and is positioned midway between thepress wheels 48. Collar 81 presents a forward opening 87 that rotatablyreceives the rearward end of a central arm 83. Arm 83 extends forwardlyfrom collar 81 and is connected to tandem wheel arms 47 at a locationlongitudinally forward of collar 81. Accordingly, instead of arms 47being connected to the outer ends of press wheels 48, they could insteadconverge to the midpoint of axle 79, and engage the axle via collar 81.Accordingly, when one of the press wheels 48 travels over an obstacle67, the midpoint of axle 79 will raise a distance equal to ½*H. Joint 65on arm 47 will thus raise a distance equal to ¼*H. Consequently, asdescribed above, the planting unit frame 37 (and opener discs 40) wouldbe raised the same distance as joint 65, ¼*H.

If both press wheels were to travel over obstacle 67 (e.g., a clump ofhard dirt), the planting unit frame 37 (and opener discs) would beraised a distance equal to ½*H, as described above. This scenario isunlikely, however, as the obstacle 67 would likely be smashed ordisplaced by gauge wheels 43.

If one or both of the gauge wheels 43 were to travel over obstacle 67with press wheel assembly 35 configured as illustrated in FIGS. 16-18,the overall vertical displacement of frame 37 would remain ½*H asdescribed above.

Referring now to FIG. 13, planting unit 36 can provide a mechanicallinkage and reciprocal movement between the gage wheels 43 and presswheel assembly in accordance with an alternate embodiment. Inparticular, tension bar 74 extends axially through frame 37 as describedabove. In this embodiment, the upper ends 66 of each gauge wheel arm 56are connected to wobble bracket 136 as described above. However, thelower segment 58 of each gauge wheel arm 56 is connected to the hub 64of the corresponding gauge wheel 43, as planting unit 36 does notinclude tandem wheel arm 47. Instead, the rear end of tension bar 74 isconnected to press wheel assembly 35 via a bell crank 163, as will nowbe described.

Press wheel assembly 35 includes a single press wheel 48 that isrotatably connected on either side to a support arm 83. Support arms 83extend forwardly from press wheel 48 and are pivotally connected to therear end of planting unit frame 37 at joint 89. A spring 171 is providedhaving a lower end connected to the longitudinal midpoint of arms 83 viaa laterally extending brace (not shown). The upper end of spring 171 isconnected to the lower end of an arm 181. Spring 171 provides shockisolation when the press wheel 48 travels over obstacle 67.

A bell crank 163 is provided having a lower end 175 that is pivotallyconnected to the rear end of tension bar 74. The upper end 177 of bellcrank 163 is pivotally connected to frame 37 via a bracket 165 thatextends upwardly and rearwardly from the rear end 88 of column 72. Therear end 179 of bell crank 163 is connected to the upper end of arm 181.An optional spring 173 connects the lower end of bell crank 163 tobracket 165, and can be placed in tension to urge the bell crank 163 torotate counterclockwise about its upper end and causing additional downpressure against press wheel 48, thereby transferring more of the rowunit weight to the press wheel 48.

It should be appreciated that upwards translation of press wheel 48causes arm 181 to translate, thereby rotating bell crank 163 clockwiseand translating tension bar 74 rearwardly as will be described in moredetail below. Conversely, upwards translation of one of the gauge wheels43 causes tension bar 74 to translate forwardly, thereby rotating bellcrank 163 counterclockwise and biasing press wheel 48 downwardly. Thedistance that tension bar 74 translates axially relative to the distancethat press wheel 48 translates vertically can be controlled by 1) thelocation on arm 83 that connects with 181, and 2) the geometry of bellcrank 163.

For instance, reducing the horizontal distance between linkages 177 and179 will associate greater bell crank rotation in response to verticaltranslation of arm 181, thus producing a correspondingly greatertranslation of tension bar 74. Conversely, increasing the horizontaldistance between linkages 177 and 179 will associate less bell crankrotation in response to vertical translation of arm 181, thus producinga reduced translation of tension bar 74. The horizontal distance betweenlinkages 177 and 179 can be empirically optimized to minimize theplanting unit height increase in response to the event of a gauge wheel43 traveling over obstacle 67 and in the event of a press wheel 48traveling over obstacle 67, as will now be described.

In particular, during operation, when one of gauge wheels 43 of plantingunit 36 illustrated in FIG. 13 travels over obstacle 67, wobble bracket136 tends to lower the opposing gauge wheel 43 a distance equal to H.However, ground 85 does not permit the opposing gauge wheel to lower.Assuming the tension bar 74 did not connect the gauge wheels 43 to presswheel assembly 35, upper ends 66 would be translated forwardly an amountthat corresponds to the planting unit being raised a distance of ½*H,while the opposing gauge wheel lowers a distance ½*H. The planting unit37 (and opener discs 40) would thus be raised a distance equal to ½*H.Such an assembly is further disclosed in U.S. Pat. No. 4,423,788, thedisclosure of which is hereby incorporated by reference.

Advantageously, the present invention links the press wheel assembly 35to the upper ends 66 and wobble bracket 136 via bell crank 163 andtension bar 74. Accordingly, the forward movement of upper ends 66 causetension bar 74 to translate forwardly, and bell crank 163 to rotatecounterclockwise. The press wheel 48 is thus caused to pivot downwardlywith respect to joint 89, thereby enabling tension bar 74 to movefurther forwardly. The geometry of bell crank 136 can be optimized suchthat half of the total ½*H increase is achieved by the gauge wheels 43at elbow 70, while the other half of the ½*H increase is achieved by thepress wheels at joint 89. The planting unit 37 and opener discs 40 arethus raised vertically a distance of ¼*H at joints 89 and 70.

If the press wheel 48 travels over obstacle 67, arm 83 pivots aboutjoint 89, and is raised at its intersection with arm 181 (or spring 171)a distance slightly less than H. The pivoting of arm 83 causes arm 181to raise, thereby biasing bell crank 136 to rotate in the clockwisedirection about Arrow B. Tension bar 74 is thus translated rearwardly,thereby lowering gauge wheels 43. The optimized geometry of bell crank163 cause half of the height increase H to be achieved by the presswheel 48, while the other half of the height increase H is achieved bythe gauge wheels 43. As a result, the planting unit frame 37, and openerdiscs, are raised a distance equal to ½*H.

The present invention contemplates that planting unit 36 illustrated inFIG. 13 can include a press wheel assembly 35 having a pair of presswheels 48 as described above with reference to FIGS. 16-18. Accordingly,if one of the rear press wheels 48 of the planting unit 36 of FIG. 10were to pass over obstacle 67, the vertical position of collar 81 wouldbe increased by a distance equal to ½*H. The height increase of collar81 would cause arm 83 to pivot about frame 37, thereby raising the arm83 at its intersection with arm 181 (or spring 171) a distance slightlyless than ½*H. The upward translation of arm 181 causes bell crank 163to rotate clockwise which, in turn, translates tension bar 74rearwardly. Front gauge wheels 43 are biased downwardly a distancecorresponding to the distance that arm 181 was raised. Bell crank 163and tension bar 74 thus provide a mechanical linkage between the rearpress wheels 48 and front gauge wheels 43.

It has been empirically determined that the geometry of bell crank 163can be optimized to raise planter frame 37 at press wheel and gaugewheel support locations 89 and 70, respectively (and thus raise theplanter frame 37 as a whole) a distance substantially equal to ¼*H. Thedepth of seed trench 45 is thus decreased a distance substantially equalto ¼*H.

It should be appreciated that frame 37 would be raised a distance of ½*Hif both press wheels were to travel over obstacle 67 (e.g., raisedcollection of hard dirt). Such a situation is unlikely, however, ascollections of hard dirt would likely be smashed or displaced whenpassed over by gauge wheels 43.

Referring now to FIGS. 14 and 15, planting unit 36 can include arm 181that is constructed in accordance with an alternate embodiment. Inparticular, arm 181 includes an upper segment 183 that is fastened to alower segment 185. A plurality of apertures 187 extend laterally throughlower segment 185 that can be matched with an aperture 189 extendinglaterally through the lower end of upper segment 183. A pin 191 isinserted through the apertures to control the planting depth of trench45. The planting unit 36 illustrated in FIG. 14 is vertically displacedas described above when a gauge wheel 43 or press wheel(s) 48 travelover obstacle 67.

The above has been described as a preferred embodiment of the presentinvention. It will occur to those that practice the art that manymodifications may be made without departing from the spirit and scope ofthe invention. In order to apprise the public of the various embodimentsthat may fall within the scope of the invention, the following claimsare made.

1 A seed planting unit comprising: a planting unit frame that carries:i. a seed trench opening assembly including a seed trench forming memberoperable to create a seed trench in a ground surface; ii. a seeddelivery assembly delivering seeds into the seed trench; iii. a seedtrench closing assembly operable to close the seed trench; and aplanting unit support assembly including A) a pair of opposing gaugewheels in mechanical communication with the frame, and B) at least onerear press wheel in mechanical communication with the gauge wheels,wherein a vertical displacement of one of the gauge and press wheels ina first direction produces a biasing force on the other of the gauge andpress wheel in a direction opposite the vertical displacement.
 2. Theseed planting assembly as recited in claim 1, wherein the verticaldisplacement has a height, and wherein the vertical displacementproduces a planting unit vertical displacement less than one-half theheight.
 3. The seed planting unit as recited in claim 1, whereinvertical movement of one gauge wheel is reciprocated by the opposinggauge wheel,
 4. The seed planting unit as recited in claim 3, whereinthe gauge wheels are connected at to the frame via gauge wheel arms thatoperate reciprocally in response to a vertical translation of one of thegauge wheels.
 5. The seed planting unit as recited in claim 4, whereinpress wheel assembly includes a pair of press wheels that operatereciprocally in response to corresponding vertical gauge wheeltranslation.
 6. The seed planting unit as recited in claim 5, whereinthe gauge wheel arms define upper ends that are connected to a bracketthat pivots in response to vertical gauge wheel translation.
 7. The seedplanting unit as recited in claim 6, wherein at least one tandem armconnects the rear press wheel assembly to at least one gauge wheel. 8.The seed planting unit as recited in claim 7, wherein at least one gaugewheel arm is connected to the tandem arm.
 9. The seed planting unit asrecited in claim 8, wherein the gauge wheel arm is connected to thetandem arm substantially at a midpoint between the press wheel and thegauge wheel.
 10. The seed planting unit as recited in claim 7, whereinthe rear press wheel assembly comprises a pair of independentlysuspended press wheels connected to both gauge wheels via acorresponding pair of tandem arms.
 11. The seed planting unit as recitedin claim 6, wherein the rear press wheel assembly includes a pair ofpress wheels connected to opposite ends of a press wheel axle.
 12. Theseed planting unit as recited in claim 11, wherein the axle is rotatablewith respect to the planting unit frame.
 13. The seed planting unit asrecited in claim 12, wherein the axle is connected at a midpoint betweenthe press wheels to the planting unit via a linkage.
 14. The seedplanting unit as recited in claim 13, further comprising: a linkagedefining a forward end and a rearward end, wherein the forward end is incommunication with the bracket; and a bell crank defining threeconnection locations, wherein the first location is connected to therearward end of the linkage, and wherein the second location isconnected to the planting unit frame, and wherein the third location isin communication with the press wheel assembly.
 15. The seed plantingunit as recited in claim 14, wherein the third location is connected tothe linkage.
 16. The seed planting unit as recited in claim 15, whereinthe linkage provides a downward force against the press wheel assembly.17. The seed planting assembly as recited in claim 16, wherein thelinkage comprises a spring providing shock isolation.
 18. The seedplanting unit as recited in claim 16, wherein the linkage comprises apair of linkage segments connected in one of a plurality of positions.19. A method for reducing seed trench depth variations during operationof a seed planting unit including 1) a planting unit frame that carriesi) a seed trench opening assembly including a seed trench forming memberoperable to create a seed trench in a ground surface, ii) a seeddelivery assembly delivering seeds into the seed trench, and iii) a seedtrench closing assembly operable to close the seed trench, and 2) aplanting unit support assembly including i) first and second opposinggauge wheels in mechanical communication with the frame, and ii) atleast one rear press wheel in mechanical communication with the gaugewheels, the steps comprising: A) causing a vertical displacement of oneof the first gauge wheel and the press wheel in a first directionrelative to the frame; C) biasing the other of the first gauge wheel andthe press wheel in a direction opposite the first direction relative tothe frame in response to step (A).
 20. The method as recited in claim19, wherein the gauge wheels are connected to the frame via gauge wheelarms having upper ends that engage opposite ends of a bracket that ispivotally connected to the frame, wherein step (A) further comprisespivoting the bracket to displace the other gauge wheel in the oppositedirection.
 21. The method as recited in claim 20, further comprising thestep of connecting the press wheel assembly to at least one of the gaugewheels via a tandem arm, wherein one of the gauge wheel arms defines alower end that is connected to the tandem arm.
 22. The method as recitedin claim 20, further comprising the step of connecting the press wheelassembly to the bracket via a bell crank that 1) is pivotally connectedto the frame at one location, 2) in mechanical communication with thepress wheel assembly at a second location, and 3) in mechanicalcommunication with the bracket at a third location.
 23. The method asrecited in claim 19, wherein the first direction is an upwardsdirection, and wherein the opposite direction is a downwards direction.24. A method for reducing seed trench depth variations during operationof a seed planting unit including 1) a planting unit frame that carriesi) a seed trench opening assembly including a seed trench forming memberoperable to create a seed trench in a ground surface, ii) a seeddelivery assembly delivering seeds into the seed trench, and iii) a seedtrench closing assembly operable to close the seed trench, and 2) aplanting unit support assembly including i) first and second opposinggauge wheels in mechanical communication with the frame, and ii) firstand second opposing rear press wheels in mechanical communication withthe gauge wheels, the steps comprising: A) causing a verticaldisplacement of the first press wheel relative to the frame in a firstdirection; and B) biasing the second press wheel in a second directionopposite the first direction relative to the frame in response to step(A).
 25. The method as recited in claim 24, further comprising the stepof: C) causing a vertical displacement of at least one of the gaugewheels relative to the frame.
 26. The method as recited in claim 25,wherein vertical displacement the gauge wheel is reciprocated by theopposing gauge wheel.
 27. The method as recited in claim 24, furthercomprising the step of connecting the rear press wheels via an axle. 28.The method as recited in claim 27, further comprising the step ofconnecting a midpoint of the axle to the frame.
 29. The method asrecited in claim 28, wherein each press wheel is independentlydisplaceable with respect to the midpoint.